Gaucher's Disease is an inborn error of glycosphingolipid metabolism that is associated with glucocerebrosidase deficiency and accumulation of glucocerebroside in reticuloendothelial organs. Current biochemical information, though extensive, does not fully explain all of the manifestations of this disease, particularly, the broad spectrum of clinical severity. This project seeks information in the following areas: 1. The physical and immunological properties of normal and Gaucher glucocerebrosidase. 2. The mechanism and kinetics of the lipid storage process, particularly as related to Gaucher cell formation and turnover. 3. Associated abnormalities in serum immunoglobulins, coagulation factors, B-12 binding proteins and serum enzymes.